Robots are increasingly being used in many different applications, including semiconductor device fabrication. A robot can be generally and non-restrictively defined as a stand-alone hybrid computer system that performs physical and computational tasks. It is a multiple-motion device with one or more arms and that is capable of performing many different tasks. It can be designed similar to human form, although most industrial robots do not resemble people at all. Robots are used extensively in manufacturing, including semiconductor device fabrication.
FIG. 1 shows a robot 100 that is used to transfer semiconductor wafers between fabrication stations, so that the wafers can have semiconductor devices fabricated thereon. The robot 100 includes a fork 102 that has left and right prongs 104 and 106 used to pick up, transfer, and put down semiconductor wafers. Via a connection 108, the fork 102 connects to an arm 110, which is connected to a motor (not shown in FIG. 1) for moving the fork 102. The fork 102 may be moved in and out, rotate, twist, as well as move from one station to another.
The motor that controls the robot 100 receives communication from an internal or external computer that provides instructions as to how and where the fork 102 should be moved. Actuators of the motor, however, may temporarily lose communication with the robot 100, such that one or more instructions for movement of the fork 102 may not properly be communicated. In semiconductor fabrication applications, this can have disadvantageous, if not disastrous, consequences.
The fork 102 of the robot 100 may hit a barrier, such as a wall, the floor, a semiconductor fabrication tool, and so on. The robot 100 may be damaged, and/or the wafers that the robot 100 is holding may become broken. Both the robot 100 and the wafers it holds are typically very expensive. Therefore, mis-communication resulting in advertent movement or motion of the fork 102 of the robot 100 can cause costly errors.
Therefore, there is a need for ensuring that the fork 102 of the robot 100 does not hit barriers. More specifically, there is a need for ensuring that the fork 102 of the robot 100 does not hit barriers in a manner that causes damage to the robot 100 or the wafers that it carries. For these and other reasons, there is a need for the present invention.